UCLA Department of Psychology

Welcome to the first issue of the Journal of Evolution and Health! The Journal of Evolution and Health is the peer-reviewed, open-access journal of the Ancestral Health Society, a community of scientists, healthcare professionals, and laypersons who collaborate to understand health challenges from an evolutionary perspective.

Children love to play. Why do they find such a frivolous activity so pleasurable and desirable? Perhaps it is not frivolous, but instead is an adaptation designed to guide proper cognitive development in human children. To understand why, I marshal evidence from different fields to build a case for play as a central behavioral mechanism of human brain and cognitive development. I start with a discussion of human evolution, focusing on the evolution of human physiology, tool-use, the human brain, and life-history strategy, and development, and how these are all connected as an adaptive suite. The anthropological and developmental evidence suggests the existence of an extended childhood adapted to establish the skills, knowledge, and understanding necessary to become a successful hunter-gatherer. I also compare human and chimpanzee brain development, and how brain-specific genes evolved uniquely in humans to foster human brain development. I conclude with the evidence from developmental psychology that even contemporary, first-world children are born with the drive to learn and develop intellectually through play. In this framework, human play can be viewed as an adaptation that guides human brain development to produce curious, intelligent and well-adjusted adults. I close by speculating on the possibility that barriers to or constraints on play may hamper intellectual and cognitive development. I focus on the important concept of developmental decanlization as a mechanism of evolutionary mismatch. I argue that more empirical study is needed to better understand the importance of play compared to other forms of education for optimal intellectual and cognitive development.

The human body—an amazing biological system that scales up fractally from its cellular building blocks—exhibits an incredible ability to self heal. Why then, are chronic diseases and degeneration on the rise in the population? Why are we sicker, more obese, and more depressed and stressed than ever before in human history? Why can’t we heal? The answers to these questions may lie in our ancestry, and modern departure from the human ecological niche. The ability to heal requires proper spatio-temporal inputs—nutrition, sleep, stress, activity, and socialization—in order for cellular signaling to occur properly across semi-permeable cell membranes. We first review key steps in the evolutionary history of multicellular life, focusing on the fundamental role of cell-cell interactions. Next, we present this as an important framework by which to understand how the entrainment of physiological signals in homeostatic mechanisms reveals new insights into the processes of disease. Examples are drawn from the evolution of metabolism, nutrition, and respiration in multicellular life. We argue that disease processes result from a mismatch between the physiological inputs an individual receives and their optimal amount and fractal distribution as determined by an individual’s ancestry. A comparative analysis is a useful tool by which to illuminate deep homologies that reveal a mechanistic account for disease processes. This cell-molecular approach provides a useful contrast to the traditional reductionist approach to disease exemplified by the human genome project. As an example, we describe how cell-cell communication drives the ontogeny and phylogeny of physiology, producing the tissues, organs, and organ systems that hierarchically serve human physiology on various levels. Modern society, with its disconnected and stress-riddled lifestyle, is increasingly failing to provide the proper inputs for healthy gene expression and physiological function. Thus, the answers to our modern health woes—physical, mental, and social—may lie in acknowledging the powerful roles that our past has played in shaping our bodies. Finding ways to provide the proper inputs of the human ecological niche in the modern day may lead to significant, perhaps staggering improvements in our health and wellness. The fractal mathematics underpinning these dynamics also serves as a metaphor for the Ancestral Health Movement, which is currently arising as a multi-cultural, multi-national grass-roots pluralistic phenomenon.

In two experiments, rats received sensory preconditioning treatment in which an auditory conditioned stimulus (CS) X was followed by visual CS A in Phase 1, and CS A was followed by an appetitive US (sucrose) in Phase 2. Rats also received presentations of auditory CS Y unpaired with other events. At test, rats looked for sucrose more following CS X than following CS Y on non-reinforced probe test trials only if the light bulb on which CS A had been presented during training was removed from the chamber at the time of testing. With the light bulb present (but unlit), rats showed nodifference in amount of nose poking between CS X and CS Y. These results suggest that rats distinguish between the explicit absence of events and lack of information

The study of human and animal behavior in psychology is almost always framed at either the associative or the cognitive level of explanation. Despite continued debate between proponents of each approach, we appear to be no closer to a consensus view than we were when the debate began in earnest in the 1960 s. Could it be that the two levels of explanation are irreconcilable? Or is it possible that both frameworks are useful, though incompatible? Perhaps these frameworks merely account for the same behaviors but at different levels of explanation, as characterized by hardware-software or genotype-phenotype analogies. This special issue provides a venue for contemporary scientists involved in this debate to express their views, and follows from a Focus Session of the same title held at the 2010 meeting of the Winter Conference in Animal Learning & Behavior.

Deeply rooted within the history of experimental psychology is the search for general laws of learning that hold across tasks and species. Central to this enterprise has been the notion of equipotentiality; that any two events have the same likelihood of being associated with one another as any other pair of events. Much work, generally summarized as ‘biological constraints on learning,’ has challenged this view, and demonstrates pre-existing relations between cues and outcomes, based on genes and prior experience, that influence potential associability. Learning theorists and comparative psychologists have thus recognized the need to consider how the evolutionary history as well as prior experience of the organism being studied influences its ability to learn about and navigate its environment. We suggest that current models of human memory, and human memory research in general, lack sufficient consideration of how human evolution has shaped human memory systems. We review several findings that suggest the human memory system preferentially processes information relevant to biological fitness, and highlight potential theoretical and applied benefits afforded by adopting this functionalist perspective.